In the past, methods to improve crop yield and quality have typically relied on fertilisers and other chemicals, or genetic breeding programs to select for beneficial traits. Alternatively, careful manipulation or control of the environmental factors during crop growth such as temperature or irrigation is almost always used to improve crop outcomes.
These systems have certain advantages, yet also certain disadvantages.
For instance, fertilisers and chemicals can lead to environmental pollution, cost money and time to apply to crops and often garner consumer disapproval.
Genetic breeding has many advantages, yet it can be a slow process, and is often difficult to control the phenotypic outcome. For instance, whilst one commercially important trait may be improved (such as disease resistance), it may come at a cost to a deleterious trait such as taste or colour.
Finally, careful control of growth conditions before harvest certainly is important. Yet less hardy plants often die due to stresses in the outdoor environment regardless of this control of growth conditions, and this leads to a net loss of production.
Historically, UV radiation has been seen as a detrimental treatment to plant seedlings. Yet, in more recent years, research has focused on treatment of certain plants with ultraviolet (UV) radiation and visible light to improve defense/protection mechanisms.
Behn et al.1 shows exposure of lettuce seedlings with filtered natural sunlight, containing UV-B, UV-A and visible light led to improved stress tolerance, but as a trade off led to a loss of biomass accumulation, thought to be due to a redirection of carbohydrate substrate from growth to secondary metabolism (i.e. protection mechanisms). Whilst the plants showed improved defense/protection, crop yield and quality diminished. 1 Europ. J. Hort. Sci., 76(2). S. 33-40, 2011, ISSN 1611-4426
WO 2012/085336 describes a device to deliver a combination of UV-A (315-400 nm), UV-B (280-315), violet and blue (400-500 nm) and red and far red (600-800 nm) light, optionally also with green and yellow light (500-600 nm). The device was used to treat tree seedlings and it was suggested this prevented transplantation shock while the plants are moved from an indoor setting to an outdoor setting for plant growth. Specifically, it discloses that the device's treatment shortened the growth cycle of tree seedlings, enhances the proportion of viable seedlings and eliminates one work phase in the growth process (e.g. removing the need for sunshade curtains), thus improving the economics of seedling cultivation. Yet, WO 2012/085336 is only focused on seedling viability and the economics of seedling cultivation, not towards improving crop yield and/or quality. Additionally, it relies on multiple UV wavebands, which may complicate the treatment process and/or may lead to undesirable traits, for instance those as described in Behn et al. All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise”, or variations thereof such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.